Field
The present disclosure relates to an organic light emitting diode (hereinafter, referred to as OLED) display device.
Description of the Related Art
Each of a plurality of pixels constituting an OLED display device includes an OLED which includes an anode, a cathode, and organic light emitting layers in between the anode and the cathode, and a pixel circuit independently driving the OLED. The pixel circuit primarily includes a switching thin film transistor (hereinafter, referred to as TFT), a capacitor, and a driving TFT. The switching of TFT charges data voltage in the capacitor in response to a scan pulse, and the driving of TFT controls an electric current amount supplied to the OLED according to the data voltage charged in the capacitor to control the amount of light emission of the OLED.
That is, the OLED display device as a self-light emitting type display device does not require a separate light source, and as a result, the OLED display device can be fabricated with a small weight and a thin film unlike a liquid crystal display device. Further, the OLED display device is researched as the next-generation display device in many different fields because the OLED display device is advantageous in terms of power consumption due to the use of low-voltage, color implementation, a response speed, a viewing angle, and a brightness contrast ratio (CR).
In the OLED display device having such advantages, differences in the threshold voltage and mobility of the driving TFT may occur for each pixel due to a process deviation, and the like. The voltage drop of a high-potential voltage VDD occurs and the amount of current driving the OLEDs varies. As a result, a luminance deviation between the pixels occurs. In general, there is a problem in that an unintended spot, stain or pattern is generated on a screen due to an initial characteristic difference of the driving TFTs. A characteristic difference due to the deterioration of the driving TFTs, which occurs while driving the OLEDs, decreases the life-span of an OLED display panel or causes an afterimage of the OLED display panel. Therefore, an attempt is continuously made to introduce a compensation circuit that compensates the characteristic deviation of the driving TFTs and compensates the voltage drop of the high-potential voltage VDD to improve an image quality by decreasing the luminance deviation between the pixels.